The present invention relates to warm air furnaces and more particularly to down flow forced air furnaces primarily adapted for mobile home use.
In the heating of mobile homes and other structures where little space is available for the furnace, special problems are experienced. The furnace is typically positioned in a closet-like space where the exterior casing is close to paneling or other wall structures. The radiant heat from the furnace must be controlled or limited to prevent damage to the structure. Also, efficiency of operation is more critical than in other applications.
Typical down draft forced air furnaces include an exterior casing, a plenum and a heat exchanger positioned within the plenum. The exterior casing includes a louvered room air return opening and defines with the plenum an air receiving chamber or blower compartment. A blower is mounted in the chamber and forces air into the plenum and through the heat exchanger. A hot air distribution chamber is defined below the heat exchanger and receives heat air therefrom. The heated air is then directed to distribution ducts.
Examples of prior warm air furnaces adapted for mobile home use may be found in U.S. Pat. No. 3,223,078, entitled WARM AIR FURNACE and issued on Dec. 14, 1965, to Miller et al; U.S. Pat. No. 3,601,116, entitled MOBILE HOME FURNACE WITH AIR CIRCULATOR OUTLET MEANS and issued on Aug. 24, 1971, to Davis; U.S. Pat. No. 3,656,470, entitled BASE ASSEMBLY FOR MOBILE HOME FURNACE AND ISSUED ON Apr. 18, 1972, to Goodgion et al and U.S. Pat. No. 3,614,949, entitled MOBILE HOME FURNACE WITH MAKE UP AIR SUPPLY MEANS and issued on Oct. 26, 1971, to Goodgion.
The furnace disclosed in U.S. Pat. No. 3,223,078 includes an exterior casing in the upper portion of which is disposed a squirrel cage blower. A plenum chamber receives air from the blower and all of the air forced into the plenum chamber passes downwardly through a plurality of heat exchanger tubes. The heat exchanger tubes are in flow communication with an air distribution chamber. The tubes are concentrically arranged around a flame chamber defined by a baffle mantle. The tubes are positioned in spaced adjacent relationship with respect to each other in a generally rectangular fashion or in a generally circular fashion. The baffle mantle is formed from an inorganic fibrous insulating material which glows upon application of heat and prevents flame contact with the heat exchanger tubes. A flame gun is supported by the heat exchanger and injects flame into the baffle mantle or flame chamber. Baffle plates extend downwardly from the top of the tubes to points spaced above the lower ends of the tubes. The baffles join adjacent pairs of the tubes. Further, the heat exchanger tubes are in supporting contact with the flame chamber. A flue extension passes upwardly from the heat exchanger at the forward end thereof and through the air receiving chamber between a louvered air intake and the blower motor. The furnace may be either gas or oil fired. The flame chamber has a constricted open top and serves as a volumetric choke. A plurality of volumetric chokes or constrictions are defined by the structure resulting in positive pressure conditions in the combustion chamber. The combustion gases pass out of the furnace in a generally S-shaped flow pattern.